Method of making an abrasive article



July 3,' 1945. A, G. SCUTT 2,379,544

' METHOD OF MAKING AN ABRASIVE-ARTICLE Filed June 24, 1943 Elf 672,607

Patenteci July 3, 1945 j METHOD OF MAKING AN ABRASIVE Aa'rrc Arthur G. Soutt, Niagara Falls, N. in, asslgnor to The Carborundum Company, Niagara Falls, N. Y., a corporation of Delaware Application June 24, 1943, Serial No. 492,057

6 Claims.

This inventionrelates to bonded abrasive articles, and more particularly to abrasive articles in which the abrasive portions of the articles are supported by metallic or other rigid means, such as metal backing plates or side plates secured to the fiat faces of abrasive sections, or metal or other rigid rings fastened to the back or inner surface of annular-shaped abrasive articles for the purpose of mounting on grinding apparatus and/or as reinforcing means. Especially the invention concems improved methods of adhesively securing these supporting plates, rings, and the like to theabrading elements of the articles.

The invention has been found particularly applicable to the making of disc-shaped grinding wheels adapted to be mounted for grinding with the fiat side face of the wheel. On suchform of abrasive article for which the invention is particularly well adapted is in the making of diamend abrasive wheels consisting of a metallic abrading element adhesively secured to a hard resin or other rigid backing plate and having a facing of diamonds on the fre flat surface of the metallic abrading element. Therefore, for purposes of simplicity and clarity, the invention will be described mostly as it pertains to the making of these abrasive articles. I

It has been customary practice for a long time tosecure the abrading element of a side grinding disc to a backing support adhesively by means of an intermediate layer (herein referred to as a tie bond) of rubber. Recently, the rubber used in the tie bond layer has been replaced by numer- Oils synthetic elastic materials such as the vulcanizable butadiene type polymers and copolymers thereof with unsaturated compounds such asstyrene and acrylic nitrile, and other resilient plastics of rubber-like characteristics. The high torsional stresses and vibrational shocks and strains placed-upon such abrasive articles during operation, and particularl upon those parts where the abrasive sections are joined to the be. ing plates, have resulted in a high percentass of failures, most of which occur because of weaknesses of the wheels at the joints between the-backing plates and the abrading elements. Inspection of numerous joints between the backing plates and the abrading elements of articles which had failed disclosed that the strength of the joint between the components was not uniform and regular throughout the area of juncture of the two parts, but that the entire strength of he joint often depended upon relatively small "portions of the overall area, which were usually disposedalong the edges of the joint.

I have discovered methods by which the adhesion of abrasive elements to their supporting or mounting means in the above type of supported. abrasive articles can be greatly improved, and whereby uniformly strong bonds can be obtained in which weak spots or areas of little or n strength are substantially eliminated, resulting in a lesser number of failures because of weaknesses which heretofore tended to cause premature dis carding of the wheels.

In accordance with the present invention I employ the same resilient rubber-like tie bonds heretofore used, but I have found that improved adhesion and stronger articles are obtained when the layer of tie bond which is interposed or positioned between the abrading element and the backing plate is provided with a plurality of vents, perforations or openings distributed over its area so as to permit the tie bond material to flow during its cure, whereby the tie bond material is subjected to an even pressure over its entire area and any unevennesses of its thickness are eliminated. These vents or openings are provided by perforating the rubber-like tie bond sheet or otherwise providing it with a number of small cutaway areas distributed over the tie bond sheet and extending through the sheet thickness. After the sheet of tie bond material has been suitably perforated or vented, the abrasive element, supporting element and intermediat tie bond layer are assembled and the tie bond vulcanized or matured by suitable treatment. Before assembly the various surfaces to be Joined are cleaned and a film of suitable adhesive applied to the surfaces to increase the strength of adhesion.

Although rubber may be used in carrying out the present process a number of synthetic resil-' ient rubber-like materials have been found to be highly suited for use as tie bond materials. One synthetic tie bond material which is highly effective is polychloroprene which has been suitably compounded. Another highly satisfactory tie bond material is the copolymer of butadiene with acrylonitrile. Among other vulcanizable synthetic elastic materials of rubber-like characteristios which are satisfactory are polyvinyl chloride, butadiene polymers, polyethylene sulfide, polybromoprene; copolymers of butadiene with styrene, methyl methacrylate, isobutylene, coumarone, indene, vinylidene chloride, chloromethacrylic ester; copolymers of chloroprene with acrylonitrile, styrene, methyl methacrylate; and: other copolymers of butadiene or halogen-' substituted butadienes with polymerizable combond sheet suitable for use in making the article shown in Figures 1 and 2 in accordance with the present invention. I

The disc-shaped, diamond-faced abrasive wheel illustrated in Figures 1 and 2 consists of an abradlng element 6 adhesively secured to a backing element or plate I by means of an intermediate layer of bonding material 8 which is rendered strongly adherent to both the supporting element and the abrading element by means of films of adhesive. In the wheel shown the abrading element 6 is composed'of a main metallic body 9 which has been provided with a metallic bonded facing ID of diamonds integrally united to the metallic body 8 so as to constitute a flat, diamond abrasive surface. As a support to provide added strength during grinding and to provide a means for mounting, the abrasive element 6 is equipped with a hard resin backing plate I adhesively attached to the supporting face I l of the abrading element by means of an intermediate layer of tie bond 8. The backing plate I is composed of a heat-hardened resin such as a phenol formaldehyde condensation product together with a suitable filler such as wood flour, mineral filler or the like commonly used in resin molding practice, and is provided with a center arbor hole i3 and four bolt holes H for fastening the backed wheel to a mounting plate on the grinding machine. (The mounting plate is not shown.)

The intermediate tie bond layer 8 of Figures 1 and 2 is further shown in Figure 3 as it is prior -to being used in combining the backing and the abrasive element and consists of a layer of soft, pliable, resilient, rubber-like material in the form of a thin sheet approximately in thickness, although the thickness may vary somewhat from these figures. By selection of the proper thickness of this-intermediate layer, the desired degree of resilience, i. e., resistance to mechanical shock, of the wheel can be closely controlled.

The tie bond layer is provided with a plurality of perforations 2 distributed over the entire area of the tie bond sheet and extending through the thickness of the layer of tie bond material.

In the specific embodiment shown, the vents consist of a number of diameter perforations approximately one inch apart uniformly distributed over the sheet. However, thetie bond vents can be given any convenient shape or size provided that they are arranged so as to extend over and affect the entire sheet of material, and may take the form of slots or grooves in the material, or the material even can be used in the form of a number of individual pieces of tie bond separated from one another by small clearance spaces, although for convenience of preparation and assembly it has been found very satisfactory to use a single one piece layer of tie bond material suitably perforated.

In carrying out the present invention the surfaces of the abrading element and the backing 2,379,044 pounds to formvulcanizable elastics; also such or supporting element are suitably cleaned of dust, oil and dirt, one or more thin coatings of cement are applied to the clean surfaces, and the elements are dried after each application of cement. After the last coating of cement has been applied and dried, the abrading element and backing are heated in an oven to atemperature of about 250 F. A cement for applying to the adjoining faces of the wheel and backing when polychloroprene tie bond material, for example, is employed can be made from vulcanizable compounded polychloroprene broken down to cement form in a solvent such as benzol or toluol. Two cements which have been found to be highly satisfactory for this purpose are onesfsold on the market as Bostik M417 and Bostik M-162.

A rubber-like tie bond material which is highly satisfactory for the present use is made of the following ingredients compounded and sheeted After the tie bond has been compounded and prepared in sheet form and has been cut to the desired size and provided with suitable vents or perforations for use with the backing plate and abrasive section, the three parts are assembled. The sheet of tie bond is placed upon the backing plate and smoothed down by running a roller over its surface to insure complete contact with the backing. The abrasive section which has been kept in an oven at 250 F. is then removed and, while still hot, is placed on the tie bond sheet and supporting plate. The assembly is centered on a mandrel to hold .the parts in place during cure and the whole placed in a hot press.

The tie bond is cured in the hot press under a quate for practicing the invention by those ordinarily skilled in the art, further details in the technique of preparing and assembling the component parts of abrasive articles of the type which have rigid backing elements secured to the abrasive portions by means of tie bonds may be had by reference to U. S. Patent No. 2,342,313, issued February 22,, 1944. Such detailed methods can be similarly employed in carrying out the various operations involved in performing the present improved method entailing the use of vented tie bond layers.

The attachment of metal, hard resin or other rigid supporting elements to abrading elements by means of perforated or otherwise vented layers of tie bond materials offers a number of advantages over prior art methods. Firstly, the present method is an improvement over a past practice in that consistent results can be hereby obtained so that in the manufacture of large numbers of abrasive articles of the reinforced or backed ime a uniform, high strength is acquired in substantially all the finished articles, so that the number of rejects due to defective joints is alpfi'eciably lowered. It has been further found in articles made by the present process the re'sultant union between the backing and the abrading element is .uniformly strong and there is a minimum of weak spots or areas within. the joint. It is. suggested that the provision of vents or perforations within the tie bond sheet results in the improvements and advantages set forth because the vents allow the escape of gases and trapped air which may be present or become trapped in the tie bond or between the tie bond' and the parts to be Joined when they are assembled, and that any solvents which maystill be present in the cement can likewise escape. The vents or perforations, by permitting the escape of the gases, air or evaporated solvents, etc., gives -the tie bond material an opportunity to flow evenly and smoothly during the period in which it exists in plastic form while being cured, so that it comes into much more intimate contact with 2. The method of making bonded abrasive articles having rigid supporting elements adhesively attached thereto, which comprises perforating a layer of resilient tie bond material with a plurality of perforations distributed over the area of the tie bond sheet, inserting a layer of said periorated tie bond material between the surfaces of the abrading element and the supporting element to be united, and heating said assembly under pressure to unite the support-,

ing element to the abrading element by means of the intermediate tie bond layer.

3. In the manufacture of abrasive articles comprising an-abrasive .element and a supporting element the steps which comprise perforating a sheet of tie bond material, assembling the 1 article with the tie bond between theabrasive the backing and abrasive surfaces and as a con-'.

sequence strongly unites thesame.

The tie bond materials employed in securing the supporting elements'to the abrasive bodies are elastic and, during the curing cycle, pass through a plastic state. In the absence of the vented areas herein provided the property of elasticity causes the tie bond to stretch during the pressure used'in curing. Slight variations in element and the supporting element, and subjecting the assemblage to heat and pressure for a suflicient length of time to cause the tie bond to flow into intimate contact with the two elements and adhesively join the elements'to form an article characterized by substantially uniform attachment over the entire area of the atthickness over the area of the tie bond material localize the elastic movement of the material and cause the material to stretch more insome' places than others and set up under conditions of local strain produced by its uneven action so that an even pressure and adhesion of the tie bond to the backing element and to the abrasive body are prevented. -The provision of vents or clearance areas within the tie bond material tached surfaces.

4. The method of making bonded abrasive articles, having rigid supporting elements ad-.

hesively attached thereto, which comprises perforating a'layer of resilient, rubber-like tie-bond substantially eliminates the above uneven elastic action and permits the plastic flow of the material during cure so as to remove slight variations in thickness and distribute the pressure employed in curing imitormiy over the area of the bond is; obtained over the entire combining area.

In the specification and claims, where the term .perforated or the term "perforatio is used the term is not to be considered as restricted to 'an y specific size, shape or arrangement of holes or clearance spacesother than that the holes or perforations are distributed over substantially the entire area of the surfaces being united.

tie bond with the result that av strong adhesive,

material, applying a thin film of suitable adhesive cement to the surfaces to be joined, inserting a layer of said perforated tie bond material between the adhesively-coated surfaces of the abrading element and the supporting element to be united, and applying heat and pressure to mature the tie bond layer and unite the supporting element to the abrading element.

5. The method of making bonded abrasive articles having rigid supporting elements adhesively attached. thereto which comprises perforating a layer of resilient tie bond material with a plurality of perforations distributed over the area of the tie bond sheet, inserting'a layer of said tie bond material between the surfaces of the abrading element and the supporting element to be united, and subjecting the said as- Havingdescribed the invention fully, it is desemblage to pressure at a. temperature sumcient to mature the tie bond and unite the supporting element to the abrading element by means of the intermediate tie-bond layer. I 6. The method of making bonded abrasive .articles having rigidsupporting' elements ad-' hesively attached thereto, which comprises perforating a layer of resilient tie bond material with a plurality of perforations distributed over the area of the tie bond sheet, inserting a layer of said perforated tie bond materialjbetween the surfaces of the iabrading eiement and the sup-5 porting elementjto be united, applying pressure to. the assemblage, and subjecting to heat to mature the tie bond and unite the supporting element to the abrading element by means of the intermediate tie bond layer.

7 ARTHUR G. 'scu'rr. 

